The California WaterFix, formerly known as the Bay Delta Conservation Plan, would build two massive tunnels beneath the Sacramento–San Joaquin River Delta for an estimated $17 billion and would take 10 to 15 years to complete. The project as originally proposed would build two tunnels to shore up the State Water Project by diverting Southern California-bound water around the fragile San Joaquin Delta.

Currently, California’s largest supply of water is dependent on 50-year-old levees. According to state officials, if a natural disaster occurred it might cause the levees to fail, allowing salt water intrusion which could contaminate the fresh water supply.

The initial plan was to build two 35-mile long tunnels from the beginning of the State Water Project near Tracy to the bank of the Sacramento River. However, in February 2018, the California Department of Water Resources (DWR) announced that WaterFix would be developed in two stages instead.

The first stage will include a single tunnel and two intakes with a capacity of 6,000 cubic feet per second (cfs) while the second phase would add another tunnel and a third intake expanding the capacity to 9,000 cfs.

Approval of WaterFix is dependent on, among other things, local water agencies agreeing to fund the project’s construction and operation. The DWR hasn’t talked enough districts into the plan to cover the entire $17 billion tab, but it believes it has enough money to afford the $10.7 billion cost of just one tunnel right now.